The invention relates to a tube for an exhaust system.
In motor vehicles, efforts are made to realize all components with a weight that is as low as possible. In this way, it is possible to save fuel during operation of the motor vehicle. One approach for weight optimization in exhaust systems consists in using tubes with tailored wall thicknesses, which are referred to as “tailored tubes.” The term “tailored wall thickness” means that in each point of the tube, the wall thickness is adapted to the stresses prevailing there. For example, in regions subject to a high mechanical stress, a wall thickness is used which is larger than in other regions subject to less stress.
Up to now, significant efforts are necessary to adapt the wall thicknesses of the tube to the respective stresses because it is very difficult to make changes in the wall thickness in the exhaust system tubes, which are usually drawn. For this reason, the wall thickness of the exhaust system tubes is mostly determined on the basis of the maximum stress acting in the respective portion, for example, to obtain the fatigue limit in a portion highly stressed by vibrations, or to ensure the process safety during welding, in case weld seams are to be provided. In particular, weld seams lead to the use of tubes having an excessively large wall thickness in exhaust systems. To be able to produce a weld seam with the usual accuracy in a process-safe manner, such as for a metal active gas (MAG) welding process which is typically used to save costs, wall thicknesses in the range of 1.0 mm to 1.5 mm are presently used. However, in view of the mechanical stability of the tube, a wall thickness of 0.8 mm would be sufficient over large parts. It can be seen here, that a considerable saving of weight could be realized by a tube having an appropriate tailored wall thickness.
Tests were performed to produce a tailored wall thickness by a local compression of a tube. However, it has been found that this method is not sufficiently process-safe for thin tubes.
The object of the invention thus consists in the provision of a tube for an exhaust system which can be produced with low expenditure to have an appropriate tailored wall thickness.